In general, when rolling a metal plate or resin plate by a rolling machine, rolling oil is supplied to a rolling contact portion between a work roll (mill roll) and the plate-like member, in order to cool the work roll or the plate-like member rolled by the work roll, or to improve rolling efficiency. Also, when it is necessary to clean soils or oxide films off the surfaces of the plate-like member, the plate-like member is passed through a cleaning tank that contains cleaning liquid.
Since the rolling oil and/or cleaning liquid thus adheres to the plate-like member after rolling, the rolling oil and/or cleaning liquid must be removed before the plate-like member is rolled up by a rolling-up device. This is because, if the plate-like member is rolled up with the rolling oil adhered thereto, the friction coefficient between the contact surfaces between plate-like member portions that have been rolled up decreases, so that there arises a problem in that the plate-like member may slide sideways along the direction of its width to thereby collide against the rolling-up device, or the plate-like member itself may rupture. Also, if the plate-like member (rolling coil) that has been rolled up with the rolling oil unsatisfactorily removed, is annealed at a subsequent process, there may occur a problem of causing local nonuniformity in annealing result, leading to a reduction in product quality. Furthermore, if the plate-like member is stored with the cleaning liquid adhered thereto, there may arise a problem of the plate-like member being corroded by the cleaning liquid.
Hitherto, a large number of methods for removing rolling oils or cleaning liquids have been proposed. For example, there are known methods in which rolling oil or cleaning liquid adhered to the plate-like member is scraped off or squeezed by means of a pair of rollers made of steel, rubber wiper of which the surface is covered with an elastic body such as rubber, a pair of rubber rollers, or a pair of porous rollers of which the surface is covered with a porous material such as nonwoven fabric. Also, as set forth in Patent Documents 1 and 2, there is another known method in which deposit such as rolling oil or cleaning liquid is blown off by jetting compressed air from a jetting nozzle toward a plate-like member.    Patent Document 1: Japanese Unexamined Patent Application Publication No. 10-8276    Patent Document 2: Japanese Unexamined Patent Application Publication No. 10-146611
However, since the above-described method for removing deposit using the rubber wiper or one of the pair of rollers makes the roller pair and the plate-like member contact with each other, there is a possibility that contact damage such as scratches may occur on the surfaces of the plate-like member. Especially when the pair of rubber rollers or pair of steel rollers is used, the deposit removing effect increases as the pressing force on the plate-like member increases, but on the other hand, the plate-like member becomes more susceptible to the contact damage. Such a problem becomes more serious as the plate-like member becomes thinner, and in some cases, it may lead to even rupture of the plate-like member.
Also, when the above-described porous rollers are used, the contact damage is a little reduced, compared with the rubber wiper, the pair of rubber rollers, or the pair of steel rollers. However, not only the deposit removing effect is reduced by hole clogging on the roller surface, but also there is inconvenience of having to perform maintenance work for eliminating hole logging.
On the other hand, because the method set forth in the above-described Patent Documents 1 and 2 is one for removing deposit in a noncontact manner, there is no possibility of causing a problem of incurring contact damage. However, because a jetting nozzle and the surface of a rolled plate are arranged apart from each other by about several millimeters to several tens of millimeters, there is a problem in that the jetting energy (jetting pressure) of air is dispersed and a sufficient deposit removing effect cannot be obtained.
Of course, if the compression pressure of compressed air to be supplied to the jetting nozzle is set to a higher pressure, the deposit removing effect would be enhanced, but the compressor for producing compressed air, air tank for storing compressed air or the like is upsized, and further, air piping and the like is forced to have a high resistance, which is undesirable from economical and practical viewpoints.
If the jetting nozzle can be brought as close to the surface of the plate-like member as possible, the dispersion of injection energy of air can be prevented to thereby efficiently remove deposit. However, if the jetting nozzle is brought too close to the surface of the plate-like member, there occurs a possibility that the plate-like member may be damaged from vibrations during rolling, vibrations during the conveyance of the plate-like member, or warpage of the plate-like member. For this reason, it has hitherto been difficult to bring the jetting nozzle close to the surface of the rolled plate within a range of several millimeters.
In recent years, in which the rolling speed (conveying speed) is becoming increasingly faster (about 800 m/min or more), even if any one of the above-described deposit removing methods is used, it would be impossible to efficiently and effectively remove deposit on the plate-like member rolled or conveyed at a high speed.